(1) Field of the Invention
The invention relates to electronic fine tuning of the frequency of musical instruments in which there is a standing acoustic wave.
(2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Acoustic standing waves in a musical instrument have both pressure vibrations and longitudinal air-velocity vibrations and are mostly confined within boundary walls of a resonant cavity. At certain points in the cavity, standing waves have velocity nodes of zero fluid velocity and maximum pressure. Between those velocity nodes are pressure nodes, which are points of zero pressure and maximum fluid velocity.
In the head joint of a conventional flute, an air-velocity node is always located at the face of the tuning plug, that is, the longitudinal air velocity is zero at the face of the tuning plug. Overall tuning is accomplished in a conventional flute by sliding the entire head joint relative to the body or by repositioning the tuning plug within the head joint, to change the length of the cavity. In a conventional instrument neither of those tuning procedures can be done note-by-note while playing music.
Many flutes are inaccurately intoned because some of the holes are used in differing combinations for producing more than one note, which requires design compromises in the positions and sizes of the holes. Overall tuning does not correct such compromises because the inaccuracies of intonation reside in the relative pitches of notes within the scale. Numerous design tricks attempt to alleviate the problem.
U.S. Pat. No. 5,808,218 discloses a wind instrument in which the resonant cavity is changed by physically moving the tuning plug with a servomechanism.
U.S. Pat. No. 4,429,609 discloses identification of a played musical note by means of a computer.
U.S. Pat. No. 5,668,340 discloses changing of the pitch of a wind instrument by electronically changing the length of a resonant cavity by injecting an audio tone into the resonant cavity.